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Synchronization in a communication system

A technology for synchronizing data and packet-switching communication, which is applied in the field of packet-switching communication systems and can solve problems such as high cost

Inactive Publication Date: 2005-07-27
CAMBRIDGE BROADBAND NETWORKS GROUP LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, this is costly both in terms of additional circuitry and in the event that the reference clock is disturbed by exceptionally loud noise, it is prone to various wireless link problems

Method used

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  • Synchronization in a communication system
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  • Synchronization in a communication system

Examples

Experimental program
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Embodiment Construction

[0042]Figure 1 shows, in block diagram form, a first embodiment of a communication network according to the invention. As shown in FIG. 1 , the communication system includes a network with a base station 1 communicating via a wireless link 2 with a plurality of customer premises equipment, one of which is shown in FIG. 3 . The base station 1 includes an indoor control unit 4 and an outdoor unit 5 . The indoor control unit 4 communicates with the outdoor unit 5 via a fiber optic link 6 . The customer's indoor equipment includes an outdoor unit 7 and an indoor control unit 8, which are connected together by an optical fiber link 9. The clock frequency of the data communication between the indoor control unit 4 and the outdoor unit 5 of the base station is about 155.52 MHz, the latter being locked to a 19.44 MHz clock. The clock frequency between the outdoor control unit 5 of the base station and the outdoor unit 7 of the client indoor equipment is about 3.5 GHz, the latter bei...

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PUM

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Abstract

A packet switched communications system and method for transmitting synchronous data from a source module (4) to a terminating module (8) over a network comprising plurality of modules (4, 5, 7, 8) interconnected via transmission links (2, 6, 9). Each module operates with a clock of nominal frequency that is not synchronized with the clocks of the other module(s) and has a single input and one or more outputs. The method includes determining the phase difference between the input clock and the output clock of each module, and transmitting the phase difference to the terminating module (8) in the network. The received accumulated phase difference at the terminating module (8) is used to lock the output clock at the terminating module to the input clock at the source module.

Description

technical field [0001] The present invention relates to packet switched communication systems and to methods for recovering clock signals in such systems. Background technique [0002] Asynchronous Transfer Mode (ATM) is a packet-based transmission medium designed to carry a wide range of traffic types simultaneously. Various communication networks, in particular fixed wireless access systems (FWA) may use ATM as a transmission medium between their modules as well as over the air link. It is desirable that such a system should be arranged to be flexible and deployable in a wide range of architectures with variable topologies. In order to minimize the cost, the physical interface type of ATM can be ATM User Network Interface (ATM UNI), which converts the ATM 155 SONET synchronous optical fiber interface into a wired UTOPIA asynchronous interface. One of the disadvantages of this design choice is the loss of physical layer synchronization between modules. This means that th...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04J3/06H04L12/54H04L12/70H04Q11/04
CPCH04L12/5601H04J3/0632H04L2012/5607H04J3/0658H04L2012/5616H04L2012/5649H04J2203/005H04J2203/0035H04L2012/5652
Inventor 约翰·D.·波特本尼迪克特·R.·弗里曼
Owner CAMBRIDGE BROADBAND NETWORKS GROUP LTD